A smoke detector is a device that senses the presence of smoke, typically as an indicator of fire. Commercial security devices issue a signal to a fire alarm control panel as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, generally issue a local audible or visual alarm from the detector itself.
Smoke detectors may be housed in plastic enclosures, typically shaped like a disk about 150 millimeters (6 in) in diameter and 25 millimeters (1 in) thick, but shape and size can vary. Smoke can be detected either optically (photoelectric) or by physical process (ionization), Detectors may use either, or both, methods.
Smoke detectors in large commercial, industrial, and residential buildings are usually powered by a central fire alarm system, which is powered by the building power with a battery backup. Domestic smoke detectors range from individual battery-powered units, to several interlinked mains-powered units with battery backup; if any unit detects smoke, all trigger even in the absence of electricity.
An ionization smoke detector uses a radioisotope to ionize air or any other gas within a chamber, and an electric current is generated via the ions created within the chamber. If smoke enters the chambers, the electric current changes. A difference in the electric current is detected and an alarm is generated.
The radioisotope in ionizing smoke detectors may pose a potential environmental hazard, if the smoke detector is damaged (e.g., in a fire), thus causing the radioisotope to be exposed. Exposure of radioactive material to the environment may pose environmental and health risks. It may thus be desirable to have systems, apparatuses, and smoke detectors that use a reduced amount of radioactive material, yet have enhanced efficiency to maintain sensitivity to smoke. This way, the environmental risk may be reduced.